1. Field of the Invention
The present invention relates to a device for detecting cut of a tape, particularly to a device for detecting cut of a tape for promptly detecting cut of a tape by detecting a difference of a revolution speed of a gear according to a tape state.
2. Description of the Prior Art
Conventionally, apparatuses like a video tape recorder, an audio tape recorder, and a reel tape reader comprise a driving system for rotating a tape reel. The driving system comprises a forward reel gear for operating a forward play mode of a tape and a reverse reel gear for reverse playing the tape. Each gear operates as a main rotating reel gear or a follower gear according to an operation mode. The tape is wound in a forward direction or a reverse direction according to the rotation of the main rotating reel gear.
In these apparatuses, a microcomputer is used for controlling a rotation of the main rotation reel gear. The microcomputer controls the main rotation reel gear to stop the rotation when a stop signal or an end signal is inputted. If the tape is cut during the operation mode, the main rotation reel gear connected with the driving system continues to rotate but the following reel gear unconnected with the driving system stops rotating because the state of the tape being cut is unrecognized. As a result, a user waits to start the operation mode for a long time frequently because the microcomputer does not recognize that the tape is cut. Thus, various apparatuses and methods for detecting a cut of a tape are proposed to detect the cut of the tape.
FIG. 1 is a schematic diagram of one conventional apparatus for detecting cut of a tape. The apparatus for detecting cut of a tape comprises a forward reel gear 100 to be rotated by a rotation driving part(not shown) during the forward play operation mode of the tape and a reverse reel gear 200 to be rotated by the rotation driving part during the reverse play operation mode of the tape. Forward reel gear 100 comprises a first photoelectric pulse generator. The first photoelectric pulse generator comprises a first rotating plate 110 to be rotated according to the rotation of forward reel gear 100 and a first photo sensor 120 installed at a predetermined position in a lower direction of first rotating plate 110. First rotating plate 110 comprises four first light reflecting portions 112 for reflecting light outputted from first light sensor 120 and four first absorbing portions 114 for absorbing the light.
Reverse reel gear 200 comprises a second photoelectric pulse generator. The second photoelectric pulse generator comprises a, second rotating plate 210 to be rotated according to the rotation of reverse reel gear 200 and a second light sensor 220 installed at a predetermined position in a lower direction of second rotating plate 120. Second rotating plate 210 comprises four second light deflection portions 212 for reflecting the light outputted from second light sensor 220 and four second absorbing portions 214 for absorbing the light.
An operation of the conventional device for detecting cut of the tape according to a construction described above is described below with reference to FIG. 1 and FIG. 2.
The microcomputer(not shown) detects the presence of an input signal(S1). When the input signal is present, the microcomputer operates first and second light sensors 120, 220.
Next, the microcomputer decides whether the input signal is to indicate the forward play operation mode(S3). If a result of the decision is true, the rotation driving part(not shown) is connected to forward reel gear 100 because forward reel gear 100 is the main reel gear(S4). If the result is false, the rotation driving part is connected to reverse reel gear 200 because reverse reel gear 200 is the main reel gear(S5).
The tape is wound around the circumferential face of the main rotating reel gear when the main reel is rotated by the rotation driving part. The following reel gear is rotated because the tape is wound around the main rotating reel gear.
Lights outputted from first and second light sensor 120, 220 arrive at first and second rotating plates 110, 210 according to the rotation of the main rotation reel gear and the following reel gear, and thus pulses are generated. The microcomputer counts a pulse repetition rate(P1) generated according to the rotation of the main rotating reel gear and a pulse repetition rate(P2) generated according to the rotation of the following reel gear(S5).
With cut of the tape, the main reel gear continues to rotate by the rotation driving part, and the following reel gear continues to rotate by inertia because the following reel gear is unconnected with the rotation driving part. Thus, the microcomputer checks whether P2 equals zero because the following reel gear is stopped(S6) first. When P2 equals zero, the microcomputer outputs a signal of the cut of the tape by deciding the tape cut state(S7). When P2 is unequal to zero, the microcomputer counts the pulses generated by the rotation of the reel gears.
When the input signal is not a signal for indicating the forward play operation mode, the microcomputer connects the rotation driving part to reverse reel gear 200 because reverse reel gear 200 is the main rotation reel gear. After that the operation operates in described order.
A conventional device for detecting cut of the tape has a complicated construction because first and second photoelectric pulse generators are installed at forward reel gear 100 and reverse reel gear 200 for counting pulses generated according to the rotation of forward reel gear 100 and reverse reel gear 200.
Also, in an operation mode, when tape is cut, the main rotation reel gear continues to rotate by the rotation driving part and the following reel gear continues to rotate by inertia. Thus, the time for detection is long because cut of the tape is detected after the following reel gear completely stops to rotate.